Heating circuit for different voltages



G. C. PEARCE HEATING CIRCUIT FOR DIFFERENT VOLTAGES Filed MaICh 19, 1945NVENTOR.

Aug. 3o, 1949.

Patented Aug. 30, 1949 HETINGI.I CIRGUIT FOB', DIFFERENT YOLTAGES Georgearcane; Dayton, Unio, assigner-'toy Gen-v emalzMotrszConlmtion.. Dayton;Ohio, a cor- Imraton oelame Application Maren 19, 1945;; seriali No.583,549

t ci. ers- 20) 1i-Glam: 1;

This invention relates toa domesticiappliance and. more particularlyAtoA heaters and warming devices.v

It is an object of my invention*V toprovidea simple heating and control1arrangement :which will' operate on either low= voltagefor* high`voltagey without any manual` change-over` sev-itali or dualfplugs;

It isv4 another object of" my' invention to pro'- 2 wise suitablhondedtothe bottom of the inner shell 2U. This retainer' cup tightly engages theouter'- periphery of' each' of the elements; and its upper rim* 34A isspun or leentA inwardly into contact" withV the cylindrical surface' ofthe' inner' shell 20; soas toiiml'y retain the sheathed heating elements26, 2Br and' 3G: n The sheathed heating" elements 26 and' 28 areconnected in parallel with each other as shownv inthe wiring vide asimple food' WarmingT device; whichY can 1,0 diagrams; Figs. 2` and 3`,The sheathed heating opmatel on either direct;v orA alternatingW`current element 301 is connected' in series with these elewithout anymanual` changeaover `switch"owcduai ments; A shunt circuit 35'isprovided for shuntplugs. ing-theheatingelement 33; This shunt circuitIt is another object 'of my inventief? pmincludesI a' thermarover-current relay` or pro'- videA awellf insulated foodl Warming;`Vdevice for l5 tector 38' including a' birnetalj actuating elementeither4` liquids or` solids' whichi cam be'L readily 4U: COHHCSF 42'; atoggle' lever t4 and a' tension cleaned1v without the v hazard? ofintroducing water t've'gle Spring- 46': into thefelectricalcircuit Theheating' elements 2S and 28 areA made of It is anotherfobject of'myfinvention` to prov such a'resi'stancetliat' they provide the desiredvide an improved heatingf andI controlling ar 20 rate o` heatingWhenronnectedto thelow voltrangement for affood-warming device whici'rwill age direct currentV source, such' as the battery autornaticallyvrmaintain thefteinperat'ure-d'esiredf` Il for` which' theyf are designed.For example, Further objectsand advantages offthe pres ifal zivoltfbattery suppl;r is contemplatedthes@ ent invention--v willfbeapparentfrom thel followresistances mayr have a resistance oi about '7.7 ingdescription; referenceibeing' had 1go-the acL 25 ohms eacfras to-provide74'- watts eachA at about company-ing drawings; whereini apreferred form3&1' amperes each; Thethermal over-currentv rev`oftliepresentfinventionisclearlyfshowm lay should have such a trippingvaluethat4 it will Inthe drawings: 0pen when the high1 voltagealternating current EigaV 1 is aA` verticalv sectional' view# thrrmgh asupplie 5U# isapplied to'Y theY circuit; This will food Warmingdevice'andlieatingrmeans"ernfody 3U Gwen-1211er lshuntA circuit 3B andplace the heating ingfoneform of myinvention; elements 2K1 and 28 inserieswith thek resistance Fig; 2V is` a: Wiring` diagram for` the;warmer soars-tc reduce-the'current flow throughA the 'ownihFgf; 1'as=connectedt`o a low voltageadielements t'.if and "28? toa sufficientamount to prerectcurrentrsource'; and ventiA them beingv damaged. Theresistance oi Fig;y 3" iS- a wiringf diagram*- for'A the warmer 35theheatingelement 3lshould'lbe selected sothat, showninFg; 1VVasconnectedtoa Iiighfvoltage togethere with? the heating elementsl 26and 25 alternatingcurrentpower'source.Y thefdesired heating.y rate willbe provided.` when The'fwar-mingfdevicefconsistsprincipailyfoifanconnected tothe particular alternating current aluminum innercylindricalA shell" 20?. forminga sourzfonwhiehit'is designed.Welllwhich is' adapted: toI receive ai removable 40 For exampleif:a.'1=10,volt alternating current food'container'fZZl.''Ilhisremovableeoontainenzz sourceis contemplated: the heating elements26 is provided withz a bail 24 If\T desired; however, andzimay give'- a:combinerliheatinggrate off l1 an'` ordinary can of! foodmayfbev'pleceddirectly,y watts, while theheating element 3u may have a inf theA wellfWithout opening;` or food@ may be resistanceofaboutiaoohmsandmaygivefalheat placed'rdirectly inthefwell Thei-innershell'z 45ing rate of 142 Watts upon ar current new of haawrappedfaroundfthelowerportionrotfits `cv about 1.4 amperes. The bimetal actuatingelellndrical surfaceA three tubular` aluminum mentfrlislplscedsufficiently-'close to' the bottom sheathedfheatina elementssZB/..Zfand'I'hese oitherretainer: cup SLthatitLWiIl-be heated'sutubular sheathedheating. elements--each1consist cientlyi principallyhyf theI heatingelement 3B of coiledi electricalv resistance* wire; auchVY as 50vil!"retainithizfrelay-or protector 38` in the open Nichrome Wire;embedded in packed-magnesium `circultpostion after theinitialcurrentsurfe. oxidewithin-rfaluminum"y tubing: Ihesefelments Whentherh'eating'V device=is connected to the are held:I tightly in.engagementrwith an outer cy alternatirig-a'current"power sourcethere-is an'. inilnrlricaisurfacel of-` thel well'A byr ani aluminumcurrent surge: througln theshuntcircuit 36 retainer; cup`32;'2which:ier:spot-voldoetmffotliersafvmdieaclnotthe-.eiementsf 28untilzvthe. relayer protector 38 trips. With the sheathed type ofheating elements a considerable initial current surge is not harmful;but, in fact is benelicial in promoting rapid initial heating. As soonas the relay or protector S8 opens and the heating element 38 is heatedlong enough to reach its operating temperature, the relay or protector38 will remain open due to the iniluence of this heat.

To control the temperature maintained by the warming device within thewell 28, there is provided a second bimetal strip 52 which is welded orbonded directly to the bottom of the retainer cup 32, so that it is inexcellent heat exchange relation with the bottom of the inner shell aswell as the removable container 22. This bimetal strip 52 is arranged sothat when it reaches the desired operating or limiting temperature itwill engage the button 54 of insulating material mounted upon the end ofthe spring strip 56 to separate the contacts 58 to open the circuit 82connecting to the power source. This will deenergize all of the heatingunits until the temperature is reduced a slight amount. This bimetaltemperature control will cycle substantially at this limiting operatingtemperature so as to maintain this temperature.

The thermal over-current relay 38 and the contacts 58 operated by thebimetal temperature control strip 52 are mounted upon an insulator 60which in turn is supported by a plurality of posts 62 fastened to thebottom of the retainer cup 32. The inner shell 2t as well as theretainer cup 32 and the switches are enclosed in an outer shell 64 whichis firmly held in spaced relation by the ilauge 66 provided at the rimon the inner well 28 as well-as the interfitting flange 68 at the upperedge of the outer shell 64 which has its rim 'l0 spun over so as totightly clamp the flange 66 against the iiange 88. gaining laccess tothe compartment between the shells. To provide further stability and toconcentrate the heat in the lower portion a spacer 'l2 of insulatingmaterial is provided which extends between the inner and outer shells 28and 64 and is supported upon the upper edge of the retainer cup 32.

A lid lll is provided for closing the well in the shell 28 and it isheld in place by a leaf spring i6 which snaps over the flange 68 at theupper edge of the outer shell 64. It is connected by a chain 'I8 to abail 88 to prevent loss. The supply con'- ductors 82 which connect tothe contacts 58 and to the heating elements 26 and 28, extend through anaperture Within the outer shell which is provided with a rubber sealinggrommet 84. Strain relief rings 88 extend tightly around the supplyconductors 82 on either side of the grommet 813 to protect the relayconnections against a direct pull on the supply conductors.

While the form of embodiment of the invention as herein disclosed,constitutes a Ipreferred form, it is to be understood that other formsmight be adopted, as may come within the scope of the claims whichfollow.

What is claimed is as follows:

l. A heating means adapted to be connected to current supplies ofdiierent potentials comprising a plurality of heating element portionsconnested in series, a shunt circuit for one of said portions, a currentresponsive thermal over-current self-resetting protector connected inseries with. and heated by the current flowing in said shunt circuit andlocated in sufficiently good heat exchange relation to one of saidheating. element This prevents liquid from portions to be heatedsuiiciently to remain open when tripped by current flowing under a highpotential but insufficiently heated in any manner at a lower currentpotential to open or remain open.

2. A heating means adapted to be connected to current supplies ofdiierent potentials comprising a plurality of heating element portionsconnected in series, a shunt circuit for one of said portions, a currentresponsive thermal overcurrent self-resetting protector connected inseries with and heated by the current flowing in said shunt circuit andlocated in suiciently good heat exchange relation to one of said heatingelement portions to be heated suiiiciently to remain open when trippedby current flowing under a high potential but insufficiently heated inany manner at a lower current potential to open or remain open, and acycling thermostatic control for limiting the temperature provided bythe heating element portions, said protector having a sufficiently lowresetting temperature to preventl resetting upon normal cycling of saidthermostatic control.

3. A heating means adapted to be connected to current supplies ofpredetermined low and high potentials comprising a plurality of heatingelement portions connected in series, a shunt circuit for one of saidportions, a current responsive snap-acting thermal overload protectorconnected in series with said shunt circuit, s-aid lprotector includinga thermal motor actuating element and a series current heater located inseries with the shunt circuit and in heat transfer relationship withsaid actuating element, said current heater having an ohmic resistancesuiiciently low to provide an insuicient heating rate upon the lowpotential to causethe opening of said protector but a resistancesufficiently high to provide a heating rate suicient to cause theopening of said protector upon the high potential, said protector beinglocated in sufficient heat tr-ansfer relationship with said one of saidheating element portions to cause said actuating element to be heatedsufficiently to remain open when tripped by the flow of high potentialcurrent, said heat transfer relationship between the protector and saidelement portions being low enough to prevent the opening or holding openof the protector under the low potential.

4. A heating means adapted to be connected to current supplies ofpredetermined low and high potentials comprising a plurality of heatingelement portions connected in series, a shunt circuit for one of saidportions, a current responsive snap-acting thermal overload protectorconnected in series with said shunt circuit, said protector including athermal motor actuating element and a series current heater located inseries with the shunt circuit and in heat transfer relationship withsaid actuating element, said current heater having an ohmic resistancesuliiciently low to provide an insufficient heating rate upon the lowpotential to cause the opening of said protector but a resistancesuiciently high to provide a heating rate suicient to cause the openingof said protector upon the high potential, said protector being locatedin suicient heat transfer relationship with said one of said heatingelement portions to cause said actuating element to be heatedsufficiently to remain open when tripped by the flow of high potentialcurrent, said heat transfer relationship between the protector and saidelement portions being low enough to prevent the opening or holding openof the protector under the low potential, and la cycling thermostaticcontrol connected in series with all of said element portions forlimiting the temperatu provided by the heating element portions, saidprotector having 'a sufficiently low resetting temperature to preventresetting upon norm-a1 cycling of said thermostatic control.

GEORGE C. PEARCE.

REFERENCES CITED Number UNITED STATES PATENTS Name Date H111 June 10,1919 Vaughan Nov. 3, 1931 Randolph Nov. '1, 1933 Greenman Apr. 24, 1934Olds Dec. 24, 1935 Kneisley May 9, 1939 Palitzsch Mar. 24, 1942

